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Canon raises the bar!

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  #21  
Old 09-19-2003, 01:35 PM
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Hmmm. Just when I was getting clear on this, I reread the links that PM posted. In one of them, Bob Atkins makes a counter-argument...

(quote)

Off the top of my head, if you use a 50/1.8 on a 10D and an 80/1.8 on a 1Ds you get the same field of view and the same speed lens. The physical aperture on the 50/1.8 is 27.78mm, on the 80/1.8 it's 44.44mm, so the 80/1.8 will give more 1.6x more background blur. However to get to the same print size the 10D image has to be enlarged 1.6x more, so the two effects cancel and you get exactly the same amount of distant background blur in the print in each case.

(endquote)


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  #22  
Old 09-19-2003, 01:41 PM
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catia catia is offline
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Toad,

What is "better" DOF depends on what you are doing with your camera. Depth of Field is just that, the distance over which the photo will "appear" in focus. If you want to be focused primarily on the subject and everything else blurred (like a portrait for example), you want a narrow, short, or small DOF. If you are shooting a landscape, you may want most everything to "appear" in focus. Therefore, you would like a wide, long, or large DOF.

DOF is a function of several factors, one of which can be related to the sensor format. The ratio of one dimension of a 35mm film frame to the corresponding sensor dimension can be used to adjust the DOF calculation for non 35mm format sensors. For the Canon 1D, 10D series of cameras, this factor is ~1.6. For the Sony ~ 3.6. What this means is for a given set of shooting parameters ( distance to subject, fstop, etc.), the Sony will require a focal length of ~ 2.3 that of the Canon to get the same DOF.

Looking at the result a different way. If I have a 100mm lens on both cameras, I will need to be 2.3 times as far from the subject with my Sony to get a DOF comparable to the Canon.

Please note, I am not saying that is bad or good. It is just the physics of the situation.

For me, a more important issue is quality of the lens (in terms of MTF and chromatic aberations) and focus accuracy (both auto and manual).

Double please note, I am not saying Canon is beter than Sony or vise-versa. I am saying there is more to the story than DOF.

Catia

Last edited by catia; 09-19-2003 at 01:49 PM.
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  #23  
Old 09-19-2003, 02:11 PM
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I apparently confused the issue with my reference to 35mm. Let me try again ( I promise, this is my last post on this subject ).

DOF (Depth of Field): The area in front of and behind a focused subject in which the photographed image appears sharp. In other words, the depth of sharpness to the front of sharpness to the front and rear of the subject where image blur in the film plane falls within the limits of the permissible circle of confusion.

Mathematically,

DOF = rear focus distance - front focus distance

Front focus distance = d • F • a2 / (f2 + d • F • a)
Rear focus distance = d • F • a2 / (f2 – d • F • a)

f: focal length
F: F number
d: circle of confusion diameter
a: subject distance (distance from 1st principal point to subject)

Now the d for a 10D is .019 and for a Sony F828 it is .008 found here. That gives a ratio of 2.3. So the disscussion in my previous post on required focal length for a desired DOF still applies.

Like I said, its the physics (or if you prefer, the math).

Catia
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  #24  
Old 09-19-2003, 02:14 PM
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Toad and Catia, On the dpreview site the 300D users have their own forum. There are 65 pages of posts from acutal 300D users. You might hop over there and ask these guys what they think. I found the posts to be very informative. There are several posts specifically from ex EVF owners converting to SLR direct view finders and their observations. I can't believe that Phil has already given these guys their own forum. There must be a bunch of them out there already.
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  #25  
Old 09-19-2003, 03:04 PM
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Kevin Connery Kevin Connery is offline
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Quote:
The forums are filled with almost 100 percent brand biased info.
True. Often misinformed as well, and that's not just brand-specific. Sadly, the most vocal tend to be the ones least worth listening to.

Toad, the "focal length multiplier" effect isn't linear in terms of DoF--that is, depth of field does not change at the same rate that the angle of view changes, and that's even more pronounced in terms of how quickly things go beyond 'not sharp'. If it did, there'd be far less visual differences between medium format cameras ("normal" lenses at 80mm to 127mm), 35mm, or larger format cameras than there actually is.

It also applies to digital cameras as well, but that's often heavily masked by the marketing-speak: the so-called 28-200 lens on the Sony 828 is actually 7.1-55mm. They avoid the appearance of a multiplier by only lying about the "focal length".

One real-world example

At my typical candid shooting distance (8'), angle-of-view (200mm "equivalent"), and aperture (f/2.8) for photographing candids, the depth of field* is

828: 3.5 inches
D60: 1.5 inches
35mm film: .9 inches

Doesn't seem like much difference, does it? Unfortunately, it doesn't show the substantial differences in how blurred the not-sharp stuff gets, and how quickly it gets acceptably sort.

As has been noted here, even a very short focal length lens CAN give a good out of focus, but the conditions in which that's practical are much more limited--will something a foot behind the subject be 'soft enough' to not be distracting? 5 feet? 10 feet? Or do you want everything in the scene sharp? Different tools for different uses.

* That'll give the same framing with the two cameras. The 828 would be at f/2.8 at 55mm; the D60 (or Rebel or 10D) would be at f/2.8 at 125mm. With my 35mm camera, it was f/2.8 at 200mm. I prefer being further than 8' away, but that's a distance I often have to use.

Exposure
Quote:
Explain to me how you are going to get the exposure correct as often witout the live histogram
Um, the same way photographers have been doing it for over 150 years? The same way 35mm photographers have been getting correct exposures for over 60 years?

Sure, the histogram is a great tool--I use it all the time, whether shooting standalone or tethered to a computer. (Heck, Imacon's Ixpress digital back doesn't even have a preview on the back; it just has a histogram display.) That doesn't mean it's not possible or practical to get good exposures without it. For the conditions the vast majority of people will be shooting in, the histogram is not a critical need. (That same vast majority of people don't want selective focus, either--they usually want everything sharp. But you can't exclude them from one argument and use them to prove a different one.)

Quote:
Believe me I used to make 200 posts a week in the DPR forums as the guru, minoltaman, parker north, and don northup, and the idiot.
I believe you.
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  #26  
Old 09-19-2003, 03:22 PM
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OK - I think that I see the relationship beween sensor size and DOF now.

Probably either camera (and dozens of others) will offer acceptable results for my needs - as I said earlier I tend to err on the side of being minimalist equipment-wise, and focus on capturing the base image and on post processing.

My gut feeling is that the swiss army knife like - all-in-1 approach of the Sony F828 will fit my philosophy better than a true DSLR will, but I will wait until the production model reviews / user feedback comes in before leaping to any final conclusions.

This has been a very informative discussion for me. Thnaks to all.
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  #27  
Old 09-19-2003, 05:28 PM
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Kevin Connery Kevin Connery is offline
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Quote:
This is very misleading and only applies to dof at best.
No. "Focal length" has a definition. Advertising the camera as having a 28-200mm lens is lying when the focal length is something completely different. The lens has a focal length of 7.1 to 55mm. That's the reality.

The manufacturers or advertising agencies might have the best interests of their customers in mind, but it's still a falsehood, a misstatement of fact: a lie.

Photographers have been dealing with this for decades: the Hasselblad 80mm lens is labeled 80mm because that's its focal length. It's not labeled 50mm because it has an angle of view similar to the 'normal' lens on a 35mm camera. Mamiya's 127mm is labeled 127mm because that's its focal length; it's not labeled 50mm either, even though it'll give a similar angle of view on their RB/RZ.

Whether you need 1mm, 10mm, 100mm, or 1000mm depends on a lot of other stuff, but the lens has a focal length, and calling it a duck doesn't make it one.


"Truth is incontrovertible. Panic may resent it; ignorance may deride it; malice may distort it; but there it is."
-- Winston Churchill
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  #28  
Old 09-19-2003, 05:45 PM
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You are quite right Kevin.

However, when I was first getting into digital, I was very grateful for the 35mm equivalents that the manufacturers posted because I at least had a concept of what 50mm, 28mm, and 135mm meant.

So even if it is misleading, I am still happy that they call it out that way. My own experience is that most of them say the "actual" focal length and then put the 35mm equiv in brackets or something.

You are right that it isn't the same thing though. Length is a measurement - not a concept.
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  #29  
Old 09-19-2003, 08:11 PM
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TwinbNJ TwinbNJ is offline
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I am not a pro by any means === It is not the image -- it is the EYE behind the lens that captures the shot.
I have seen images taken with throw away camera's & instamtics that are better then pro's and some of us here !!!!

So that said and done --- I think the original post to this thread --- though lost in contreversy ---- has merrit. I am an AVID sony owner and user with over 10.000 images in six years of Sony digital images under my belt. My sister has done a lot of research on the Canon (with over 4 years of digital under her belt) on this camera and is looking forward to this purchase. So even if we are twins with different photo needs, I know I look forward to this purchase and the opportunity to use the new camera!

Always choose what is BEST FOR YOU !!!!!!!!

No matter HOW many pictures you take or how popular YOUR site is
It will always be the eye NOT the camera !!
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  #30  
Old 09-19-2003, 08:35 PM
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TwinbNJ TwinbNJ is offline
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Quote:
Originally posted by photomauler
Almost lal of his remarks to follow were incorrect propaganda. Did you read some of the preposterous stuff he posted?
propaganda is in the eye of the beholder ---as is the eye of the lens


sissy is smart and knows her photo needs.

Still can't wait to take this baby for a test ride!!!!!!!


Thanks for your reply PM --- always glad to hear YOUR opinion --- one sony guy to the next --- now don't let this out OK !!!!!!
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